CN101295629B - Methods to eliminate M-shape etch rate profile in inductively coupled plasma reactor - Google Patents

Abstract

An inductively-coupled plasma processing chamber has a chamber with a ceiling. A first and second antenna are placed adjacent to the ceiling. The first antenna is concentric to the second antenna. A plasma source power supply is coupled to the first and second antenna. The plasma source power supply generates a first RF power to the first antenna, and a second RF power to the second antenna. A substrate support disposed within the chamber. The size of the first antenna and a distance between the substrate support are such that the etch rate of the substrate on the substrate support is substantially uniform.

Description

Method for Eliminating M-shaped Etch Rate Distribution in Inductively Coupled Plasma Reactor

technical field

The invention relates to a substrate processing chamber. More specifically, the present invention relates to methods for improving etch rate uniformity in inductively coupled plasma reactors.

Background technique

Plasma reactors used to fabricate semiconductor microelectronic circuits can employ RF inductively coupled fields to maintain plasmas formed from process gases. Such plasmas are useful in performing etch and deposition processes. Typically, a high frequency RF source power signal is applied to a coil antenna near the roof of the reactor chamber. A bias RF signal is applied to a semiconductor wafer or workpiece support on a susceptor within the chamber. The power of the signal applied to the coil antenna primarily determines the chamber plasma ion density, while the power of the bias signal applied to the wafer determines the ion energy at the wafer surface. A problem with such coil antennas is the relatively large voltage drop across the coil antenna, which can have adverse effects in the plasma. This effect becomes more acute as the frequency of the source power signal applied to the coil antenna increases because the resistance of the coil antenna is proportional to frequency. In some reactors this problem is solved by limiting the frequency to a low range such as 2 MHz. Unfortunately, at such low frequencies, RF power couples poorly to the plasma. Stable high density plasma discharge is often easier to achieve at frequencies in the range of 10 MHz to 20 MHz. Another disadvantage of operating at lower frequency ranges (eg 2 MHz) is that these components, such as impedance matching networks, are larger in component size and thus more cumbersome and costly.

Another problem with coil antennas is that efficient inductive coupling to the plasma is generally achieved by increasing the number of turns of the coil, which creates a greater magnetic flux density. This increases the inductive reactance of the coil, and since the resistance (consisting mainly of the plasma resistance) remains constant, the circuit Q (ratio of circuit reactance to resistance) increases. This in turn leads to instability and difficulty in maintaining impedance matching during changing chamber conditions. Instability is particularly the case where the coil inductance is large enough that, with the combination of stray capacitances, self-resonance occurs around the frequency of the RF signal applied to the coil. Thus, the inductance of the coil must be limited to avoid these latter problems.

One limitation of coil antennas (conventional as well as interleaved types) on the roof of a chamber is that the mutual inductance between adjacent conductors in the antenna is generally in the horizontal direction—roughly orthogonal to the vertical direction in which RF power must be inductively coupled into the plasma. This is an important factor limiting the spatial control of energy deposition into the plasma. The aim of the present invention is to overcome this limitation in spatially controlled inductive coupling.

Typically, for "inner" and "outer" coil antennas, they are physically distributed radially or horizontally (rather than constrained to discrete radii), such that their radial positions spread out accordingly. This is especially true in horizontal "pancake" configurations. Thus, the ability to change the radial distribution of the plasma ion distribution by changing the relative distribution of applied RF power between the inner and outer antennas is limited. This problem is especially significant when processing semiconductor wafers with larger diameters (eg, 300 mm). This is because as the wafer size increases, it becomes more difficult to maintain a uniform plasma ion density across the wafer surface. The radial distribution of plasma ion density can be easily controlled by adjusting the radial distribution of the magnetic field applied from the overhead antenna. It is this field that determines the plasma ion density. Thus, as the wafer size increases, a greater ability to control or adjust the radial distribution of the applied RF field is required. Thus, it is desirable to increase the effectiveness of the distribution of applied RF power between the inner and outer antennas, and in particular to accomplish this by confining each of the inner and outer antennas to discrete or narrow radial positions.

Contents of the invention

Description of drawings

The invention is illustrated by way of example and not by way of limitation, in the accompanying drawings:

Figure 1 is an inductively coupled plasma reactor with two differently adjustable single power sources connected to inner and outer coil antenna outputs, respectively, according to one embodiment.

FIG. 2 is a flow chart illustrating methods for improving etch rate uniformity in the reactor of FIG. 1 according to one embodiment.

FIG. 3 is a graph illustrating etch rates of a conventional reactor and a reactor according to an embodiment.

FIG. 4 is a graph illustrating etch rates for different coil diameters according to one embodiment.

5 is a graph illustrating etch rates for a chamber gap of 5" and a chamber gap of 6", according to one embodiment.

6 is a graph illustrating etch rates for a coil diameter of 12" and a coil diameter of 17", and a chamber gap of 6", according to one embodiment 5.

Detailed ways

The following description sets forth numerous specific details, such as examples of specific systems, components, methods, etc., to provide a good understanding of several embodiments of the invention. It will be apparent, however, to one skilled in the art that at least some embodiments of the present invention may be practiced without these specific details. In other instances, well-known components or methods have not been described in detail or are presented in simplified block diagrams in order to avoid unnecessarily obscuring the present invention. Accordingly, the specific details set forth are exemplary only. Particular embodiments may be varied from these exemplary details and still be conceived within the spirit and scope of the invention.

Methods and apparatus for processing substrates are described. An inductively coupled plasma processing reactor has an inner coil antenna and an outer coil antenna disposed adjacent to the chamber roof. A single power source has two differently adjustable outputs connected to the inner and outer coil antennas respectively. The diameter of the outer coil antenna and the gap between the substrate support and the chamber roof in the chamber were adjusted to reduce the "M-shaped" etch rate distribution in the inductively coupled reactor.

Figure 1 is a block diagram of an inductively coupled plasma reactor according to one embodiment. The reactor chamber 102 is defined by cylindrical side walls 104 and a flat top 106 . A substrate support 108 may be disposed within the reactor chamber 102 oriented facing the chamber roof and centered on the chamber's axis of symmetry. The substrate support 108 may be positioned a distance h below the top 124 .

The vacuum pump 110 cooperates with an exhaust outlet (not shown) of the chamber 102 . A process gas supply 112 supplies process into the interior of the chamber 102 through a gas inlet 114 . Those skilled in the art will recognize that the process gases can include different compositions, for example, halide gases for polysilicon etch, fluorocarbon gases for silicon dioxide etch, or silane gases for silicon chemical vapor deposition processes , Chlorine-containing gas for metal etching. The gas inlet 114 is illustrated as a single tube in FIG. 1 , and may be realized by complex structures such as multiple inlets in practical applications.

These gases will support the plasma used to process the substrate 116 under the influence of RF power induced into the chamber 102 from the antenna 130 . With suitable precursor gases, plasma treatments that can be performed can include not only etching, but also deposition such as chemical vapor deposition.

The pedestal 108 may include a conductive electrode 118 coupled to a bias RF power source 122 through an impedance matching network 120 . Chamber sidewalls 104 may be metal such as aluminum, while roof 106 may be a dielectric such as quartz. In other embodiments of the invention, the top 106 may be flat, but may also be domed or tapered.

According to another embodiment, the top 106 may be a semiconductor rather than a dielectric. The semiconductor material of the top 124 may have optimal conductivity so that it acts as a window from the antenna 130 to the RF induction field as well as an electrode. Where IR 106 may be employed as an electrode, it may be grounded (not shown) or may be connected to an RF power source (not shown) through a matching network (not shown). Chamber 102 and/or antenna 130 may have a non-cylindrical shape (eg, a cuboid shape with a square cross-section). Substrate 116 may also be non-circular (eg, square or other external shape). Substrate 116 may include a semiconductor wafer, or other object such as a masked reticle.

As shown in FIG. 1 , the antenna 130 may include a first antenna 148 and a second antenna 150 adjacent to and on the roof 106 of the chamber 102 . According to one embodiment, the first antenna 148 may be concentric with the second antenna 150 . The first antenna 148 may be an inner coil antenna with the same axis as the chamber 102 . The second antenna 150 may be an outer coil antenna with the same axis as the chamber 102 . The outer coil antenna 150 may thus have a diameter D2 that is greater than the diameter D1 of the inner coil antenna 148 illustrated in FIG. 1 .

The RF power source assembly 132 may include an RF generator 134 connected to an impedance matching network 136 . According to one embodiment, impedance matching network 136 includes series capacitor 138 and variable shunt capacitor 140 . Those skilled in the art will recognize that impedance matching network 126 is not limited to the circuit shown in FIG. 1 . Other circuits are possible that achieve a similar effect of producing two different power levels at a single frequency from a single power source.

Impedance matching network 136 may include a first RF output terminal 144 and a second RF output terminal 146 . The first RF output terminal 144 may be connected at the input of the series capacitor 138 . The second RF output terminal 146 may be connected to the output of the series capacitor 138 . Those skilled in the art will understand that the circuitry of matching network 136 illustrated in FIG. 1 is not a complete matching network circuitry. It is shown for illustration purposes only. Adjusting the variable shunt capacitor 140 can distribute more power to one output terminal or the other, depending on the adjustment. Thus, the power levels at the two output terminals 144, 146 can be adjusted differently.

The first output terminal 144 may be connected to the outer antenna 150 and the second output terminal 146 may be connected to the inner antenna 148 . Thus, terminals 144, 146 are connected to inner and outer antennas 150, 148, respectively. The dual output power source assembly 132 can be used with any plasma reactor having inner and outer antennas.

Several factors can affect the etch rate profile of substrate 16 . Among these factors are the diameter D1 of the inner coil antenna 148 , the diameter D2 of the outer coil antenna 150 , and the gap h between the substrate 116 /substrate support 118 and the roof 106 of the chamber 102 . By adjusting diameter D, diameter D2, and/or gap h, the "M" shaped etch rate profile of substrate 116 can be eliminated or significantly reduced. According to one embodiment, diameter D2 and chamber gap h may be modified/tuned to improve the etch rate profile of the substrate.

2 is a flowchart illustrating a method for improving etch rate uniformity in the reactor of FIG. 1 while eliminating the "M" shaped etch rate distribution of substrate 116 . At 202, an inductively coupled plasma reactor is provided. The chamber has inner and outer antennas, both powered by a differently adjustable power supply as shown in FIG. 1 . At 204, a substrate support is positioned in the chamber at a gap h from the top of the chamber.

At 206, the diameter of the outer antenna is adjusted to increase the etch rate distribution uniformity of the substrate disposed on the substrate support in the chamber. According to one embodiment, the diameter of the outer antenna increases, for example, from 15" to 17".

At 208, the chamber gap h is adjusted to increase the uniformity of the etch rate distribution of the substrate. According to one embodiment, the chamber gap h increases from 5" to 6".

According to another embodiment, the diameter and chamber gap h are adjusted and balanced such that the etch rate distribution of the substrate is substantially uniform, thereby substantially eliminating the "M" shaped etch rate distribution.

3 is a graph illustrating a comparison of etch rate distributions from a conventional reactor and from a reactor according to one embodiment. The etch rate profile 302 is the result of a conventional inductively coupled chamber with an outer coil antenna diameter of 15" and a chamber gap of 5". Etch rate profile 304 is a result of an inductively coupled chamber according to one embodiment. For purposes of illustration, one embodiment of an inductive coupling chamber has a chamber gap of 6" and an outer coil antenna diameter of 17". As shown in FIG. 3, the etch rate distribution is substantially uniform on the surface of the substrate. Significantly eliminated the previous M shape.

Figure 4 illustrates different etch 3 rate distributions based on a constant chamber gap h and different diameters D2. Variations in the diameter D2 of the outer coil antenna 150 affect the M-shape peak position. When the chamber gap h is small, the effect of the diameter D2 of the outer coil antenna 150 becomes significant due to the short horizontal length of dispersion caused by the limited vertical chamber height. The M-shaped peak moves toward the edge of the substrate as the diameter D2 increases, thereby increasing the etch rate at the edge of the substrate 116 and improving etch rate uniformity.

Figure 5 illustrates different etch rate distributions based on different chamber gaps h (5" and 6") and a constant outer coil antenna diameter D2 (15"). Variation of the gap h gives the plasma more room to spread horizontally/ Chance. Thus, the M-shaped peaks move toward the center as the chamber gap h increases, eventually merging to form a single peak at the center. On the other hand, there are more surfaces at the chamber wall 104 due to the longer diffusion length Chance of recombination loss. The etch rate at the edge decreases rapidly.

Figure 6 is a graph illustrating etch rate profiles for a 12" coil diameter and a 17" coil diameter with a chamber gap of 6" according to one embodiment. For an outer coil diameter of 12", the etch rate at the edge of the substrate appears to be Did not increase. However, for an outer coil diameter of 17", the etch rate is equivalent to that at the center of the substrate.

Although the operations of the methods are described and shown herein in a particular order, the order of operations of each method may be changed such that particular operations may be performed in reverse order or may be performed at least in part with other operations present . In another embodiment, instructions or sub-operations of distinct operations may be performed intermittently and/or alternately.

In the foregoing specification, the invention has been described with reference to specific exemplary embodiments. It will, however, be evident that various modifications and changes can be made without departing from the broader spirit and scope of the invention as set forth in the claims. Accordingly, the specification and drawings are to be regarded in an illustrative rather than a restrictive sense.

Claims (16)

1. equipment that is used to handle substrate comprises:

Chamber with top;

First and second antennas adjacent with described top, described first antenna is concentric with described second antenna, wherein, described first antenna comprises having at least 17 " first solenoid of diameter;

The plasma source power supply, it is coupled to described first and second antennas; And

Substrate supports, it is arranged on described indoor, wherein, the distance between described substrate supports and the described top is 6 at least ",

Wherein, the distance between the size of described first antenna and described substrate supports and the described top makes the rate of etch of the substrate with 300mm diameter on the described substrate supports even, and does not have the M distribution of shapes.

2. equipment according to claim 1, wherein, described second antenna comprises second solenoid.

3. equipment according to claim 2, wherein, the diameter of described first solenoid is greater than the diameter of described second solenoid.

4. equipment according to claim 1, wherein, the rate of etch of the inner region of described substrate depends on the size of described first antenna.

5. equipment according to claim 1, wherein, the rate of etch of the exterior domain of described substrate depends on the distance between described substrate supports and the described top.

6. equipment according to claim 1, wherein, described plasma source power supply also comprises:

The supply of RF power; And

Impedance matching network, it is coupled to the supply of described RF power,

Wherein, but described impedance matching network comprises first and second RF output of the power level with different adjustment, and described RF output is connected to described first antenna, and described the 2nd RF output is connected to described second antenna.

7. equipment according to claim 6, wherein, described impedance matching network produces a RF power level of described first antenna and arrives the 2nd RF power level of described second antenna,

Wherein, can differently regulate the described RF power level that is applied to described first and second antennas respectively is applied to the RF field from described first and second antennas with control radial distribution.

8. one kind is used for comprising in the method for responding to coupling process chamber processing substrate:

The location and the first and second adjacent antennas of top of described chamber, described first antenna is concentric with described second antenna, wherein, described first antenna comprises having at least 17 " first solenoid of diameter;

In described chamber substrate supports is set, wherein, the distance between described substrate supports and the described top is 6 at least "; And

Regulate the size of described first antenna and the volume of described chamber, make that the rate of etch of the substrate with 300mm diameter on the described substrate supports is even, and do not have the M distribution of shapes.

9. method according to claim 8 also comprises:

Described first and second antennas are coupled in the plasma source power supply,

Wherein, but described plasma source power supply comprises first and second RF output of the power level with different adjustment, and described RF output is connected to described first antenna, and described the 2nd RF output is connected to described second antenna.

10. method according to claim 8, wherein, the volume of regulating described chamber also comprises:

Regulate the distance between the described top of described substrate supports and described chamber.

11. method according to claim 8, wherein, described second antenna comprises second solenoid.

12. method according to claim 11, wherein, the diameter of described first solenoid is greater than the diameter of described second solenoid.

13. method according to claim 9, wherein, the rate of etch of the inner region of described substrate depends on the size of described first antenna.

14. method according to claim 10, wherein, the rate of etch of the exterior domain of described substrate depends on the distance between described substrate supports and the described top.

15. method according to claim 8 also comprises:

Distance between the diameter of described first solenoid of balance and the top of described substrate supports and described chamber is to carry out uniform etching to described substrate.

16. ex vivo treatment chambers such as induction coupling comprise:

Chamber with top;

First and second antennas adjacent with described top, described first antenna is concentric with described second antenna;

Be arranged on the substrate supports in the described chamber, described substrate supports is used to support the substrate of 300mm;

Be used for device that a RF power is fed to described first antenna and the 2nd RF power is fed to described second antenna; And

Wherein, described top separates a distance with described substrate, and wherein, described distance is adjustable, and wherein, described first antenna has adjustable diameter; And

Wherein, described first antenna comprises first solenoid, and described second antenna comprises second solenoid, the diameter of described first solenoid is greater than the diameter of described second solenoid, the diameter of described first solenoid is at least 17 ", the distance between described substrate supports and the described top is at least 6 ", and wherein, the rate of etch of the wafer of the 300mm on the described substrate supports is even, and does not have the M distribution of shapes.

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